Process of producing a surrogate for tannin



' UNITED stares.

rarest orriee.

CARL GRAF, OF COLOGNE-RODENKIRCHEN, GERMANY, ASSIGNOR, BY MESNE ASSIGN-MENTS, TO THE CHEMICAL FOUNDATION, INC., A CORPORATION OF DELAWARE.

PROCESS OF PRODUCING A SUBROGATE FOR TANNIN'.

No Drawing.

To all whom it may concern:

Be it known that I, CARL GnAr, a subject of the King of Wurttemberg,residing at Cologne-Rodenkirchen, Germany, have invented certain new anduseful Improvements in Processes of Producing a Surrogate for Tannin, ofwhich the following is a specification.

The present invention relates to a process of producing a surrogate fortannin, adapted to be employed both alone for itself and also mixed withthe extracts of the vegetable tanning materials hitherto employed forthe manufacture of leather ready for use, without thereby altering inthe least the ordinary manner of working.

The starting material of the process is tar, be it common coal-tar orbrown coal-tar, or different kinds of tar extracted from peat or wood.The important elements for the present process are separated from thetar by a preliminary treatment with water or with alkalis, neutral orbasic salts or other equivalents. The preliminary treatment with thesematerials has, compared to that with water, the advantage, that thechief material is better utilized thanby treatment only with water. Fromthe tar a liquid will be separated to which sulfates of aluminium andcopper are added. In lieu of the sulfate of aluminium we may also usefor ex ample, however, the other equivalents such as potassium alum,chrome alum and ammonium alum. The liquid obtained in this way isemployed for tanning leather. As a residue-a tough, pitch-like massremains, from which by a repeated treatment with the above-namedmaterials surrogates for tannin may be prepared.

It is possible, to introduce in the preliminary treatment the materialsto be added in the aftertreatment, such. as the sulfates of aluminiumand copper. We thereby obtain a product that may, in case of need, alsobe made use of for tanning leather. The result obtained is, however,less favorable by far than if the materials in question are added onlyin the after-treatment. more, possible to attain a tanning action by theemployment of only one of the sulfates referred to. But, if only sulfateof copper be used, the tanning action is considerably weaker and theleather is less filled, than will be the case if sulfate of aluminium orany of the sulfates or alums, applicable in its Specification of LettersPatent.

Application filed March 11, 1916.

It is, further.

Patented May 3, 1921. Serial No. 83,613.

place be added. On the contrary, by the addition of sulfates ofaluminiumand the like the liquid is improved to such a degree,

that it presents qualities similar to those of,

extracts of vegetable substances. If, on the contrary, the sulfate ofcopper be omitted, theleather acquires a dark-gray color, which 1s, inmost cases, not wished for.

The process may be carried out both in the cold and at an increasedtemperature, it

being, however, hastened if the temperature rises. Y

As an example, in 100 lbs. of water 20 to 25 lbs. of sulfite of soda orequivalent material will be dissolved. To this solution 50 lbs. of tar,e. g. beech-wood tar are added,

when the whole mixture is agitated for some time. Now Sto 10 lbs. ofsulfate of aluminium or 6 to 7 lbs. of alum are added un der contlnuousstirring; the stirring operation is then stopped and l to 2 lbs. ofsulfate of copper are added, whereupon the stirrer is continued. Theliquid obtained by this treatment may at once be employed for tanning ormay be inspissated by evaporation. I

What I claim is:

1. That process of producing a surrogate for tannin, which comprisestreating about 50 lbs. of tar with a solution comprising 100 lbs. ofwater and 20 to 25 lbs. of sulfite of soda or its equivalent; adding andthoroughly mixing with this mixture 8 to 10 lbs. of sulfate of aluminumor its equivalent;

adding to the mixture thus obtained 1 to 2 lbs. of sulfate of copper.

2. That process of producing a surrogate for tannin, which comprisestreating tar with an aqueous solution of an alkali or its equivalent;and thoroughly mixing with the liquid thus obtained a metallic sulfateor mixture'of metallic sulfates.

3. That process of producing a surrogate for tannin, which comprisestreating tar with an aqueous solution of an alkali or its equivalent;separating the liquid thus obtained; and treating said liquid withsulfate of copper and sulfate of aluminum.

In testimony whereof I affix my signature in presence of two witnesses.

CARL GRAF.

Witnesses:

, T. F. LoUN'rs,

H. HENDEL.

